The present invention relates to a liquid crystal display device, and more particularly to a so-called “partial transmission type” active matrix liquid crystal display device.
In an active matrix type liquid crystal display device, on a liquid-crystal-side surface of one of respective transparent substrates which are arranged to face each other in an opposed manner while sandwiching liquid crystal therebetween, gate signal lines which are extended in the x direction and are arranged in the y direction in parallel and drain signal lines which are extended in the y direction and are arranged in the x direction in parallel are formed, and regions surrounded by these respective signal lines are formed as pixel regions.
A thin film transistor which is driven by scanning signals from a one-side gate signal line and a pixel electrode to which video signals are supplied from a one-side drain signal line through the thin film transistor are provided to each pixel region.
Further, with respect to such a liquid crystal display device, a so-called partial transmission type liquid crystal display device includes a light transmission portion which constitutes a region which allows light from a backlight disposed at a back surface side to pass therethrough and a light reflection portion which constitutes a region in which an external light such as sun beams are reflected on each pixel region.
The light transmission portion is formed of a region which constitutes the pixel electrode using a light-transmitting conductive layer and the light reflection portion is formed of a region which constitutes the pixel electrode using a non-light-transmitting conductive layer having a light-reflecting function.
However, with respect to the liquid crystal display device having such a constitution, it has been pointed out that the contrast of display is largely reduced particularly when the liquid crystal display device is used in a light reflection mode.
As a result of the study of causes of such phenomenon, inventors of the present invention have found that the pixel electrode which is formed on the light reflection portion is constituted of the non-light-transmitting conductive layer and hence, a capacitive element or the like is generated at a lower-layer side of the pixel region in many cases whereby the height of the pixel electrode which also functions as a reflection film differs with respect to a substrate.
The difference in height of the reflection film results in the difference of layer thickness of liquid crystal in such portions and this brings about the lowering of contrast.
For example, it has been known from a result of an experiment that when the difference of 0.2 μm is generated with respect to the height of the reflection film, the contrast is halved.
The present invention is made in view of such circumstances and it is an object of the present invention to provide a liquid crystal display device which can enhance the contrast.